Dry-type transformers are core power equipment for distribution lines, favored for high dielectric strength, strong short-circuit resistance, environmental friendliness, fire/explosion prevention, and low maintenance. Professional, scientific installation techniques, proper cooling management, and moisture protection are key to ensuring safe and reliable operation.
1. Core Installation Requirements
- Personnel Qualification: Installation technicians must master professional skills, with systematic training on equipment structure and installation specifications.
- Pre-Installation Preparation: Confirm equipment integrity (windings, bushings, accessories), check installation environment (ventilation, cleanliness, humidity), and prepare tools (insulation testers, lifting equipment).
- Problem Handling: Timely resolve and summarize issues during installation (e.g., loose connections, improper positioning) to avoid hidden dangers affecting subsequent operation.
2. Cooling Methods & Operational Guidelines
Dry-type transformers adopt two main cooling methods, each with specific application scenarios and limitations:
(1) Natural Air Cooling (AN)
- Operating Principle: Relies on natural convection and radiation to dissipate heat, no additional cooling equipment required.
- Performance: Supports long-term continuous operation at rated capacity with stable efficiency and low noise (≤55dB for medium-capacity models).
- Applicable Scenarios: Small-to-medium capacity transformers (≤1000kVA) in normal load conditions, such as residential or office building power distribution.
(2) Forced Air Cooling (AF)
- Operating Principle: Equipped with axial fans to actively blow cold air over windings, enhancing heat dissipation efficiency.
- Performance: Increases transformer output capacity by 50% (e.g., a 630kVA transformer can carry 945kVA).
- Applicable Scenarios: Intermittent overload (e.g., industrial peak loads) or emergency overload (e.g., temporary power grid shortages).
- Critical Note: Overload causes a sharp increase in load loss and impedance voltage, leading to uneconomical operation and accelerated insulation aging—long-term continuous overload is strictly prohibited.
3. Moisture Protection: Key to Avoiding Insulation Failures
While dry-type transformers have inherent moisture resistance, their open structure (coupled with relatively lower insulation levels of some domestic models) makes them susceptible to moisture intrusion:
(1) Basic Moisture Resistance Parameters
- Applicable Humidity: Reliable operation is achievable at a relative humidity of ≤70%.
- Insulation Resistance Threshold: When the insulation resistance drops below 1000Ω/V (e.g., 400MΩ for 400V transformers), it indicates severe moisture—immediately stop trial operation and dry the equipment.
(2) Moisture Protection Measures
- Environment Control: Avoid installing in high-humidity areas (e.g., unventilated basements, coastal areas without protection) or environments with frequent moisture condensation.
- Long-Term Idle Protection: If the transformer is not used for an extended period, seal the winding ends with moisture-proof covers and regularly measure insulation resistance (monthly at minimum).
- Drying Treatment: For damp equipment, use hot air drying or vacuum drying to restore insulation resistance to the standard before putting it into operation.
4. Key Operational Reminders
- Do not exceed the rated capacity for long-term operation under natural air cooling; switch to forced air cooling only when temporary overload is necessary.
- Regularly inspect cooling fans (for AF models) to ensure they start/stop normally based on temperature, avoiding fan failure-induced overheating.
- Combine moisture protection with daily inspections: Check for condensation on windings or enclosures, and promptly improve ventilation if humidity exceeds the limit.
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